【推荐1】It was 2005 and scientists in Cape Town made a shocking discovery. Their tracking data showed a great white shark moving from South Africa to Australia and back again in a near straight line. It was the fastest transoceanic return migration ever recorded and it was carried out with near pinpoint accuracy. Today, it’s well known that sharks make yearly returns such as this to specific locations, but how exactly they do it has escaped consensus.

A group of scientists from Florida State University has taken on the question and concluded that sharks have an internal, GPS-like navigation system that allows them to read the Earth’s geomagnetic field. To conduct the research, the team first got 20 juvenile bonnethead sharks in St George Sound off the Florida Panhandle, and placed them in a small pool surrounded by copper wire. The wire allowed the researchers to create a custom magnetic field in the centre of the pool. Exposed to the magnetic field from the capture location, the sharks swam in random directions at leisure; but when exposed to the geomagnetic field that would be found 600 kilometres south of that spot, they swam north in a “homeward orientation”.

Researchers have suspected that sharks and sawfish detect magnetic fields since the 1970s, but the exact mechanism by which they do so, and the prevalence of this skill in nature has proven elusive, partly because it’s so difficult to study. “We’ve known for some time that sharks have the ability to detect the magnetic field, but this is the first time it has been tested successfully,” says Bryan Keller, a scientist at the US National Oceanic and Atmospheric Administration. “We expect these abilities are also observed in other species, like the great white, which migrate 20,000 kilometres out and back to the same spot.” The results mean that some sharks can be added to the growing list of animals that navigate by magnetic sensation, which includes sea turtles, lobsters and birds.

With the shark navigation system now demonstrated, scientists want to understand the mechanism behind it. Two theories have emerged: some researchers believe that it depends on an iron mineral called magnetite; others believe it’s based on a magnetic-field-sensing molecule in the retina (视网膜) of the eye called cryptochrome. Both theories, or a combination of the two, are plausible. Magnetite has been isolated from many animal tissues, while evidence from studies in birds suggests that they sense the inclination of the magnetic field using cryptochrome molecules in their retinas; the direction of the field is transmitted by the optic nerve to the brain, which allows them to “visualize” north and south. But scientists don’t yet know the precise location of the cryptochrome receptors, or the brain centres that process the information on the magnetic field. There’s more work to do to truly understand these masterful navigators.

【推荐1】In 1985, scientists reported a change in the atmosphere, a hole or thinning of ozone (臭氧) over Antarctica. Scientists were not sure what was causing.

Most scientists believe that man-made chemicals are destroying the ozone. They also have found signs of ozone loss in other parts of the atmosphere.

Ozone is found both in the air we breathe and in the upper atmosphere. Near the earth, ozone in the air is a danger to life. It is a waste product. But ozone found 10 to 50 kilometres up in the atmosphere protects life on earth. Ozone forms in the atmosphere through the action of solar radiation (太阳辐射). Once formed, the ozone blocks harmful radiation from reaching the earth. Scientists say a reduction in ozone and an increase in the harmful radiation will cause many more cases of skin cancer and will harm crops, animals and fishes.

The report said it is about 8 degrees colder 15 kilometres above earth than it was in 1979. Scientists think the first loss of ozone reduces the amount of solar energy the atmosphere can take in. This cools the atmosphere, increases ice cloud production and leads to more ozone loss.

Scientists found signs the ozone problem has spread. The study shows that the loss of ozone over the areas with larger population in North America and Europe was at least three times greater than scientists had thought. The ozone levels reduced much more seriously during winter months than in warmer months. This is not surprising because the amount of ozone in the atmosphere changes with the temperature.

An international effort is being made to stop the loss of ozone in the atmosphere. But many experts fear that the effort will not produce results fast enough to prevent harm to life on the earth.

【推荐3】It’s a structure that isn’t finished, yet two million people visit it every year. Antoni Gaud í began building his church, La Sagrada Família, in 1883 — and work continues to this day and it is expected to be finished in 2026, a hundred years after Gaud í’s death.

The architect grew up fascinated by the natural wonders of the countryside. Early in his career, Gaud í experimented with many styles but eventually developed his own ideas about architecture. The natural world was the main inspiration for Gaud í’s designs. “Nothing is art if it does not come from nature,” he believed. Gaud í understood that the natural world is full of curved forms, not straight lines. With this idea in mind, he based his structures on nature.

The architect’s love of nature guided the design of La Sagrada Família. Gaud í designed the inside of La Sagrada Família to feel like a forest. Inside the church, pillars rise up like trees. This theme continues outside. The outside of the church is decorated with sculptures of wildlife. For example, a turtle (a symbol of the sea) and a tortoise (a symbol of the land) are carved into the base of two columns.

Gaud í died in 1926. Before his death, he made three-dimensional models of his plans for the building, hoping that others could complete his masterpiece. Many of these models were lost during the Spanish Civil War, but some survived. These models have helped Gaud í’s successors. For example, Mark Burry, an architect from New Zealand, uses computer technology and the surviving models to bring Gaud í’s plans to life.

Gaud í’s work illustrates a timeless truth. As the architectural historian Joan Bassegoda wrote: “The lesson of Gaud í is … to look at nature for inspiration … Nature does not go out of fashion.” In fact, you might say Gaud í’s architectural style was ahead of its time. The architect’s nature-inspired designs can be seen as an early example of the modern science of biomimetics — a science that uses designs in nature to solve modern problems.